Augmented reality (AR) is a field of computer applications which deals with the combination of real world images and computer generated data. Many augmented reality applications are concerned with the use of live video imagery which is digitally processed and augmented by the addition of computer generated graphics. For instance, an augmented reality user may wear translucent goggles through which the user may see the real world as well as computer-generated images projected on top of that real world. An example of augmented reality is the yellow first-down line seen in television broadcasts of American football games. In this example, the real-world elements are the football field and players, and the virtual element is the yellow line which is drawn over the image by computers in real time.
In another example, virtual chess pieces may be overlaid on top of an empty chess board that is depicted as a camera image. The computer that overlays the virtual chess pieces must know where the camera is relative to the chess board in order to know how to augment the image correctly. One way to achieve this is through the use of markers, which may be a two dimensional bar code such as the circular shot code, or any asymmetrical pattern. Markers are put in the scene so that when these markers are recognized in the camera image, the computer rendering the virtual chess pieces knows the position and angle to render virtual chess pieces and draw them over the camera image so that the virtual chess pieces appear natural to the viewer looking at the camera image.